Latest advancement in function of digital cameras is really amazing. These days, many digital cameras are capable of recognizing the face of a non-specific person, as well as the face of a specific person. Also, some digital cameras can recognize a moving face in a through-the-lens image of the camera successively from time to time, thereby tracking the face in the image to be shot. Thus, further progress in function of digital cameras is being attempted.
It is known in the field of face recognition technique that a resolution and a signal/noise (SN) ratio of the face play an important role in recognition accuracy. For example, an insufficient resolution or a poor SN ratio of the face leads to an unclear feature of the face, resulting in degraded recognition accuracy. The resolution and the SN ratio depend on a setting of the camera. In other words, adjustment parameters of the camera are key factors with respect to recognition accuracy.
Conventional face recognition techniques thus far developed include controlling an adjustment parameter of a camera so as to facilitate recognition of a face. For example, PTL 1 discloses a technique of adjusting a focusing point, exposure, lighting, and zooming of a camera on the basis of an evaluation result of quality of a shot image data. Also, PTL 2 discloses a technique of controlling an adjustment parameter of a camera on the basis of a recognition result of a face. The latter technique includes controlling the diaphragm of the camera depending on a position, size, and orientation of the face. For example, the diaphragm is opened wide for a large face, and narrowed for a small face.